Reprocessing method by fluoride volatility process using solid-gas separation

Abstract

Fluorine or a fluorine compound is subjected to a reaction with a spent oxide fuel to produce fluorides of uranium and plutonium, and the fluorides are recovered using a difference in volatility behavior. The spent oxide fuel is subjected to a reaction with an HF gas, whereby uranium, plutonium and most impurities are converted into solid fluorides having low valences or remained as oxides to inhibit volatilization thereof, and then in an F 2 fluorination step, the HF fluorination product is subjected to a reaction with a fluorine gas in two stages: one at a low temperature and the other at a high temperature, whereby a certain amount of gaseous uranium and volatile impurities are separated with plutonium kept in a solid form in the first stage, and mixed fluorides of remaining uranium and plutonium are fluorinated into hexafluorides at the same time in the second stage. By such a reprocessing method, plutonium enrichment can be adjusted, uranium and plutonium can be purified, and steps are simplified as well. In addition, reactors are hard to be corroded or deteriorated.

1. A reprocessing method by a fluoride volatility process using solid-gas separation in which fluorine or a fluorine compound is subjected to a reaction with a spent oxide fuel to produce fluorides of uranium and plutonium, and recover uranium and plutonium as the fluorides using a difference in volatility behavior, the reprocessing method comprising the steps of:
 HF fluorination of the spent oxide fuel in the reaction thereof with a hydrogen fluoride gas using a fluidized bed furnace operated in a temperature range of 350 to 430° C., thereby converting uranium and plutonium compounds and most impurities in the spent oxide fuel into nonvolatile solid fluorides or oxides having low valences to inhibit volatilization thereof; and 
 F 2  fluorination of the HF fluorination product in the reaction thereof with a fluorine gas which reaction is controlled in two stages: the first stage at a lower temperature using a fluidized bed furnace operated in a temperature range of 350 to 430° C. and the second stage at a higher temperature using a fluidized bed furnace operated in a temperature range of 730 to 800° C., thereby separating an arbitrary amount of gaseous uranium hexafluoride and volatile impurities with plutonium kept in a solid form in the first stage, and fluorinating the mixed fluorides of the remaining uranium and plutonium into hexafluorides at the same time in the second stage. 
 
     
     
       2. The reprocessing method by a fluoride volatility process using solid-gas separation according to  claim 1 , wherein a raw material for uranium enrichment is produced by purifying the UF 6  from the first stage and trapping purified UF 6  alone with at least one cold trap, and a raw material for MOX (mixed oxide) fuel is produced by adjusting the ratio of UF 6  and PuF 6  in the mixed fluorides obtained from the second stage to form an enrichment adjusted-mixture and trapping said enrichment adjusted-mixture of UF 6  and PuF 6  with at least one cold trap.